The present invention relates generally to the field of microwave/millimeter wave couplers, and more particularly to waveguide couplers for dielectric waveguides.
Conventional microwave circuits utilize rectangular metal waveguides, or stripline or microstrip conductors. However, for applications requiring higher frequencies near and in the millimeter wave range, the fabrication cost and/or the circuit power loss become prohibitive. The fabrication costs increase because the stripline and microstrip length dimensions must be proportional to the millimeter wavelengths they are propagating. The increased power loss occurs because the skin depth for the current flow decreases with increasing frequency thus causing a significant resistance increase in the line.
Accordingly, dielectric waveguides become an attractive alternative. However, such dielectric waveguides and the couplers used therewith still require machining, and the fabrication process is tedious and time-consuming. The machining referred to is required because prior art dielectric waveguides tend to be relatively thick, and are fabricated using processes that make it difficult to control the tolerances on the waveguide. Thus, the dielectric waveguides must be machined to insure proper dimensions. Also, when forming a dielectric waveguide coupler wherein the waveguides are brought into close proximity, a slot must be accurately machined between the waveguides with proper dimensions. Thus, it can be seen that such dielectric waveguides and couplers are not amenable to mass production techniques.